Dual-tone multi-frequency signaling (also known as DTMF) is a telecommunications technology for transferring information between telephone devices and telephone switching centers by means of in-band audio tones sent over voice frequencies. Simply put, DTMF signaling translates audible tones from pressing keys on telephone keypads into readable information that telecom companies use to process incoming phone calls.
名为 Bell 系统的通讯公司网络在1963年发明了 DTMF。随后以“Touch-Tone”商标的形式用于按键电话。DTMF 主要用于本地交换电话信号，不过它也让远程通话变为可能，现在 DTMF 被通讯企业和呼叫中心广泛使用。
DTMF 将8个不同的音频分配至键盘的行和列中。每个拨号行都是低音频，每个拨号列都是高音频。当按下对应某个数字或符号的按键后，电话会产生同时包含高频信号和低频信号的音调。然后这个独一无二的信号对被传送至本地交换机并被解码，确定拨打的号码是什么以及如何正确转接。DTMF 可以通过电话线、互联网和无线电设备传递。
The primary function of dual-tone multi-frequency signaling is identifying the dialed number and process information from customers. DTMF is employed in various industries ranging from telecommunications (inbound/ outbound call centers) and financial institutions (banks and credit card companies) to insurance and healthcare organizations. In call centers, DTMF signaling is mainly used to process user requests, obtain identification information, and route phone calls based on the keypad entries made by the caller. In addition, the DTMF technology is used in conjunction with IVR (Interactive voice response) and ACD (Automated call distribution) systems to navigate in-call menus and gather sensitive customer data.
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使用 DTMF 信号具有多种优势，例如：
- Higher security
When it comes to obtaining user input, dual-tone multi-frequency signaling provides a higher level of security. It reassures callers that their sensitive data (like credit card information, social security numbers, etc.) are protected and safe from malicious intents. As the human ear cannot interpret DTMF tones, sensitive customer information remains isolated from agents and call recording systems.
- Reduced probability of errors
- Improved call center metrics
Obtaining user input via dual-tone multi-frequency signaling can also improve several inbound call center metrics, such as Average Handling Time (AHT). Since agents don’t need to repeat user details back to the caller to confirm the accuracy of the input, the average duration of an interaction with a caller is reduced. In addition, the increased security provided by DTMF can contribute to improved customer satisfaction levels.
脉冲拨号和 DTMF 拨号的区别是什么？
Pulse dialing and dual-tone multi-frequency (DTMF) dialing are the two systems used in telephone signaling to identify the telephone number that a caller dials. In pulse dialing, pulses are generated by rapidly connecting and disconnecting the telephone connection. Pulse dialing indicates each digit in the phone number by a series of clicks that corresponds only to that digit. Thus 1 is represented by one click, 2 by two clicks, and so on. The numbers are dialed with a short gap between pulses in order to identify one digit from the next. Pulse dialing technology is no longer actively used.
DTMF 拨号使用不同音调代表不同号码。因此它无需为每个数字发送多个信号，只需发送一个信号即可。在发明 DTMF 信号之前，电话通信网络依靠的是脉冲拨号。但是脉冲拨号有一个缺点，它只能用于本地联系，如果拨打长途电话则需要接线员转接。推出 DTMF 后，按键拨号成为主要拨号方法，逐渐取代了脉冲拨号（以及使用脉冲拨号的旋转号盘电话）。虽然如此，多数使用音调拨号的电话系统也能识别并接通脉冲拨号。
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Frequently Asked Questions
What is dual-tone multi-frequency signaling?
Dual-tone multi-frequency signaling (DTMF), also called touch-tone, is a system used for telecommunication signaling over an active telephone line in the voice frequency band between communication devices. Whenever a number is dialed, the DTMF is decoded by the local exchange in order to route the call. DTMF systems use eight different frequency signals transmitted in pairs (one high frequency and one low frequency) to represent 16 different numbers, letters, and symbols.
What is dual-tone multi-frequency signaling used for?
Today, the DTMF signaling technology is widely used in the call center industry to route incoming calls using the keypad entries made by the caller and process user requests. When paired with Interactive Voice Response (IVR), DTMF provides automated self-service menu selection and gathers sensitive customer data. As a result, it has a number of advantages, such as the reduced probability of errors, higher security, and improved metrics (reduced average call handling time).
What is the difference between pulse dialing and DTMF dialing?
Pulse dialing and dual-tone multi-frequency dialing (tone dialing) are the two methods used in telephone signaling to recognize the dialed number. Pulse dialing uses different signal pulses to indicate the phone number dialed by a caller, while DTMF dialing uses specific tones to indicate the number. Since the introduction of DTMF, pulse dialing has lost its significance. Tone dialing has now become the standard for telephone companies worldwide.